Hemodialysis machines are utilized by persons having insufficient or inoperative kidney functions. The machines may be used at a health facility or in the patient's home. The machine attaches to the patient through an extracorporeal circuit of blood tubing to a dialyzer having a pair of chambers separated by a thin semi-permeable membrane. The patient's blood is circulated through one of the chambers. The hemodialysis machine maintains a constant flow of a dialysate through the second chamber. Excess water from the blood is removed by ultrafiltration through the membrane and carried out by the dialysate to a drain.
A typical hemodialysis machine provides a pair of hoses which connect to the dialyzer and include a source of incoming water, a heat exchanger and heater for bringing the water to a required temperature, a source of a dialysate concentrate or concentrates which are introduced into the water in a predetermined concentration and necessary pumps, pressure regulators, a deaerator, flow controllers and regulators. In an acetate dialysis system, only one concentrate is utilized, while in the more common bicarbonate dialysis systems, two concentrates, acidified and bicarbonate are utilized.
After use, the hoses are removed from the dialyzer and connected to a bypass which couples the two hoses together. It is then necessary to clean the dialysate from the machine and the various tubes, hoses and other elements and to clean/disinfect/sterilize the various lines and parts of the machine.
Numerous chemicals are utilized for cleaning, disinfecting and sterilizing hemodialysis machines. The cleaning, disinfecting, sterilizing treatments will generally be designated as chemical treatments hereinafter. Some of the more common chemicals are bleach, formaldehyde, vinegar, Actril and Renalin. (Actril and Renalin are registered trademarks of Renal systems, a Division of Minntech Corporation of Minneapolis, Minn.). Before any of the chemicals are introduced into the hemodialysis machine, the hemodialysis machine must be pre-rinsed. Next, the selected chemical is proportioned with water and either cycled to drain or allowed to remain in the hemodialysis machine for a desired dwell period. Dwell periods can be a few minutes, overnight or several days. Following any chemical treatment, the hemodialysis machine is again rinsed to ensure removal of residual chemicals. The operator generally will perform a manual chemical check to confirm that all chemicals have been removed.
These chemicals are hazardous to the patient and the operator must be extremely careful not to inadvertently dialyze with any of these chemicals remaining in the system. Although some apparatus may have safety devices which require certain conductivity of the dialysate, there are occasions in which improper concentrations have been utilized and serious injury or death to a patient has occurred. Therefore, safety is of utmost concern.
An improved disinfection system is disclosed in U.S. Pat. No. 4,789,467, assigned to the present assignee. This disinfection system discloses an improved cleaning system with enhanced safety features with vent and check valves utilized to ensure that disinfectant is not drawn into the hemodialysis machines.